A device such as a smartphone, tablet or other mobile terminal may support one or more radio access technologies for communicating over a wireless cellular network. For example the device may support one or more of the 2G, 3G and LTE (Long Term Evolution) technologies. A radio access technology (or “RAT”) is a manifestation in a device and/or network of a particular set of standardized specifications, comprising standardized protocols for communicating over the network. For example 2G, 3G and LTE technologies are defined in the various releases of the 3GPP (3rd Generation Partnership Project) standard. Each of the radio access technologies can be used for both voice over a dedicated voice channel and data over a general purpose packet-based data channel.
In a 3GPP environment, the radio access technology used by the device at any given time is subject to precise rules specified in the standard.
With the release 8 of the 3GPP specification, a feature called ETWS (Earthquake and Tsunami Warning System) was introduced. With release 9 of the 3GPP specification, a feature called CMAS (Commercial Mobile Alert System) was introduced. With release 10 of the 3GPP specification a feature called EU-Alert is introduced.
All of these three systems are used to inform a user of a device of possible threats like an earthquake that just has happened or an expected tsunami by way of a PWS message. Each of these three systems is commonly referred to as a Public Warning System (PWS). ETWS is the Japanese system, while CMAS is the US system and EU-alert will be the European system.
These three Public Warning Systems are described in more detail in the document “3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Public Warning System (PWS) requirements” Serial No. 3GPP TS 22.268 specification.